The present disclosure relates to a memory element storing information, based on any change of electrical characteristics observed in a memory layer including an ion source layer and a resistance change layer, and to a memory device.
A semiconductor nonvolatile memory popularly used for data storage has been a NOR or NAND flash memory. Such a semiconductor nonvolatile memory, however, has been pointed out that there are limitations on microfabrication considering the need for a high level of voltage for writing and erasing, and the limited number of electrons for injection to a floating gate.
For overcoming such limitations on microfabrication, a next-generation nonvolatile memory currently proposed is a resistance change memory such as ReRAM (Resistance Random Access Memory) or PRAM (Phase-Change Random Access Memory) (for example, see Japanese Unexamined Patent Application Publication Nos. 2005-197634 and 2009-164467. These memories (memory elements) are each configured to include a memory layer between upper and lower electrodes. The memory layer includes a resistance change layer and an ion source layer. Through application of an electric field to the memory layer by voltage application to the upper and lower electrodes, mobile atoms move in a direction corresponding to the direction of the electric field. The migration of the mobile atoms as such causes a change of resistance between the electrodes so that writing and erasing of data are performed. To be specific, during writing of data, a large number of mobile atoms are introduced from the ion source layer into the resistance change layer, thereby reducing the resistance of the resistance change layer. During erasing of data, by application of a voltage inverse to that applied during writing of data, the mobile atoms introduced into the resistance change layer are moved to the ion source layer side. In the resulting resistance change layer, the electrical conduction path is completely erased so that the resistance change layer is restored to the state before writing of data.